Members of this protein family are HemK (PrmC), a protein once thought to be involved in heme biosynthesis but now recognized to be a protein-glutamine methyltransferase that modifies the peptide chain release factors. All members of the seed alignment are encoded next to the release factor 1 gene (prfA) and confirmed by phylogenetic analysis. SIMBAL analysis (manuscript in prep.) shows the motif [LIV]PRx[DE]TE (in Escherichia coli, IPRPDTE) confers specificity for the release factors rather than for ribosomal protein L3.